In order to derive non-linear wave parameters from radar altimeter data it is necessary to model the return from the sea surface. Most models assume a Gaussian point target response for the radar, whereas in practice it was found for the SEASAT altimeter that the response was non-Gaussian. The effect of a non-Gaussian point target response on the retrieval of non-linear wave parameters is examined here, using a model based on a Gram-Charlier series. It is found that if the transmitted pulse width is sufficiently small then a non-Gaussian point target response has little effect on the retrieval of non-linear wave parameters.